Internet Protocol

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Internet Protocol

• Internetworking Lab 1

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Why Internet?
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Protocols for Inter-network

• TCP/IP protocol suite
• TCP /UDP layer 4 Transport layer
• IP network layer
• Forward packets from network to network
• Unique address which is globally recognized
• Why not MAC/Physical addresses
• Routing ( algorithms, decisions, tables )

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Internet Protocol - Goals

• Single seamless communication
• Physical network details to be hidden from
  applications
• Hardware details
• Software details
• Addressing mechanism to locate the
  network/machine (independent of MAC/Phy address)

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Internet Protocol Goals

• Based on the location of the network forward
  the packets
• For this purpose use routing algorithms and
  tables

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Solution IP functions

• Provide an addressing mechanism
• IP addresses
• IP layer ( network layer) to provide Routing and
  forwarding mechanisms
• Is not Reliable No guarantees
• Best Effort Delivery

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IP Address

• 32 bits or 4 bytes
• Each byte 255 decimal FF (hex)
• Typical address 129.21.21.3
• Dotted quad, dotted decimal
• Two parts
• Network id locates the network used in
  routing
• Host id identifies the host in the network

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Classes of IP address

• Class A
• Network id is in 1st byte, host id in the rest 3
• Class B
• Network id is in first two bytes, host id in the
  last 2
• Class C
• Network id is in the first three bytes, host id
  in the last byte
• Class D and E special cases

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Classes of IP addresses
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Identifying class
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Number of networks and hosts
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Specific IP addresses
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Network Mask

• The network mask (subnet mask)
• where there are 1s indicates the network ID
• where there are 0s indicates the host ID
• Examples
• for a class A address 255.0.0.0
• for a class B address 255.255.0.0
• for a class C address 255.255.255.0

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IP functions
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Fragmentation in IP
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Fragmentation in IP

• Identification
• used to determine which fragments belong to each
  other
• Flag
• D flag 0 data may be fragmented
• 1 data may not be fragmented
• Fragment offset
• indicates where a fragment belongs in the
  complete message measured in octets

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Fragmentation field
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IP properties

• Unreliable
• Connectionless - ?
• Best Effort